Past lives caught in the dust of trees

Standard I’m cur­rently work­ing at the Annals of Botany to help out with their social media side. There’s a bit more to it than subtly drop­ping links to their site, like this one. At the moment I’m strug­gling with the Facebook integ­ra­tion, but there’s a fun side too. I wouldn’t have browsed AoB if I’d not been hired, and that means I would have missed out on papers like Phytoliths in woody plants from the Miombo wood­lands of Mozambique by Julio Mercader and his team at Calgary. I’ll admit the art­icle title doesn’t say much to the lay­man, but it’s actu­ally some­thing deeply cool that I didn’t find out about till my MPhil.

If mega­liths are big stones and micro­liths are small stones like arrow­heads, then phyto­liths are clearly phyto-stones. Phyto– in this case mean­ing plant.

Phytoliths are micro­scopic stones formed in some plants. When a plant’s roots draw up water they also draw up the min­er­als dis­solved within it. In the case of the silica this gets pulled out of the water and depos­ited either in the cells or between the cells. The exact shape of the phyto­liths var­ies on the part of the plant the silica is depos­ited in, the avail­ab­il­ity of silica and, most excit­ingly for archae­olo­gists, the spe­cies of the plant.

Phytoliths are use­ful because nor­mally bio­lo­gical mater­ial doesn’t hang around long in the soil. Once some­thing is dead it’s lunch for some­thing else. Phytoliths are bio­lo­gical mater­ial but not organic, so they don’t break down in the same way. Mercader et al. are clear that’s is not an unam­bigu­ous relal­tion­ship. Time still has an effect, but it’s easier to find phyto­liths than it is to find organic remains for plants. Still as use­ful as they are, phyto­liths alone are not enough. A hand­ful of phyto­liths under a micro­scope would just look like a nobbly (or smoothish) thing. If you haven’t seen what a baobab phyto­lith looks like, you’re not likely to guess from simply look­ing at the phyto­lith and this is where Mercader et al step in.

Elephants in Miombo woodland. Photo by Jussi Mononen.

Elephants in Miombo wood­land. Photo by Jussi Mononen.

If you’re inter­ested in study­ing the palaeoe­co­logy of Africa in the past you’ve been rel­at­ively lim­ited to north of the equator. Mercader spot­ted that the biggest phyto­chor­ion (plant eco­sys­tem) south of the Sahara is the Miombo wood­lands. It’s huge. It runs from Angola and Namibia in the west to Mozambique in the east and from the Tanzanian shores of Lake Victoria in the north to Botswana and South Africa in the south. The dom­in­ant tree is Miombo, hence the name, which refers to a num­ber of trees of the same genus, but with dif­fer­ent spe­cies. Obviously it’s a cru­cial zone for under­stand­ing the eco­logy of sub-Saharan Africa, but no-one has described the phyto­liths of the region.

Miombos Botanical Transect after Mercader et al.

The area stud­ied was a tran­sect through the forest between the Lake Niassa shore at Metangula and the high­lands at Njawala, a dis­tance of 50km and a rise from 465m above sea-level to 1841 above sea-level. They also used indi­gen­ous col­lect­ors to sample the flora in a 5km radius around Metangula and Njawala. They estim­ate they got over 90% of the spe­cies used by the nat­ive peoples. Given that a lot of usage is likely to be dom­in­ated by rel­at­ively few spe­cies, that’s a lot of plant mater­ial. There’s then a LOT of list­ing and descrip­tion of phytoliths.

The com­mon fea­ture that amazes me is how small many of these phyto­liths are. Some are just 20–40 μm long. A micro­metre (μm) is one thou­sandth of a mil­li­metre. Despite this Mercader et al, point to the phyto­liths at the other end of the scale, some are around 200μm in length and over half are over 50μm. This means if you use stand­ard tech­niques to sieve for phyto­liths using a 50.238 to 63.246μm cut-off, you’ll miss all these lar­ger phyto­liths. That’s going to mat­ter if what you want to find evid­ence of a ‘Zambezian’ forest at an archae­olo­gical site.

It’s the sort of sci­ence that is easy to over­look. The authors don’t con­clude that whole text­books need to be re-written or that our under­stand­ing of Africa’s past has to be rebuilt from scratch. It’s also the kind of sci­ence that’s easy to whine about. Here they are, pick­ing flowers to exam­ine tiny stones in the stems rather than just appre­ci­at­ing the beauty.

But it’s also the kind of sci­ence that increases the amount of beauty and mys­tery in the world.

Until I took my MPhil, I was com­pletely ignor­ant of phyto­liths. I could view the same plants an archaeo­bot­an­ist, but saw a lot less. Before I read this paper I didn’t know that that the Miobos wood­lands were unex­amined. Knowing that these things are out there opens up new pos­sib­il­it­ies for what can be done. At Çatal­höyük they’re examin­ing phyto­liths left behind in what are almost shad­ows of woven bas­kets to flesh out details of human life in the past. In the case of this paper, it provides a bench­mark for meas­ur­ing future study­ing against. It’s detailed, metic­u­lous and some­times opaque to the non-specialist, but it’s also a descrip­tion with last­ing value. Currently pub­lic­a­tions are often judged on cita­tions garnered over a few years. That misses the value of this paper as it will be import­ant for dec­ades. Indeed, if this eco­sys­tem sud­denly becomes a tar­get for eco­nomic devel­op­ment it could even be import­ant for cen­tur­ies as a snap­shot of the cur­rent state of the Miombos woodlands.

If you want to see the phyto­liths they found, you can down­load the paper for free.

ResearchBlogging.orgMercader, J., Bennett, T., Esselmont, C., Simpson, S., & Walde, D. (2009). Phytoliths in woody plants from the Miombo wood­lands of Mozambique Annals of Botany, 104 (1), 91–113 DOI: 10.1093/aob/mcp097

Photo credit: Elephants in Miombo wood­land. Photo by Jussi Mononen.

Do we need an Industrial Archaeology?

Cromford Canal

Cromford Canal. Click for lar­ger image.

It’s easy to take a World Heritage Site for gran­ted when it’s on your door­step. I had thought of shoot­ing a short port­fo­lio of Cromford for a com­pet­i­tion. They required ten pho­tos. After look­ing into the pro­ject I’ve decided that the com­pet­i­tion isn’t going to hap­pen for me, but a short photo essay on Cromford, or pos­sibly the Derwent Valley Mills, remains an inter­est­ing idea.

Industrial Archaeology can get short shrift from other archae­olo­gists. Often there’s writ­ten records, plans and for some places oral accounts of work at a site. Is Archaeology neces­sary? Mark Henshaw, the Archaeology Dude, makes a good argu­ment that Archaeology can draw mul­tiple lines of evid­ence to inform his­tor­ies of the past. I wouldn’t dis­count that, and I think his point, Archaeology isn’t just about dig­ging, is very import­ant from an American per­spect­ive because there Archaeology is seen as a branch of Anthropology. In the UK you’re more likely to see Archaeology paired with History or Classics. So do we really need Industrial Archaeologists when there so many Early Modern Historians.

I think another factor Archaeology brings is spa­tial think­ing. Looking at the early days of the pro­fes­sion­al­isa­tion of Archaeology in Britain, one of the fea­tures is an attempt to dis­tin­guish Archaeology from History by tak­ing on ideas of Geography. People like OGS Crawford were keen to emphas­ise that Archaeology stud­ied human activ­it­ies in space as well as time. Again, in the UK, when Processualism was tak­ing off in the USA, the British aca­dem­ics took inspir­a­tion from it, but also from the ‘New’ Geography.

The Manager's House, Cromford.

The Manager’s House, Cromford.

Applying this prac­tic­ally, it’s easy to say what the pos­i­tion­ing of the Factory Manager’s house, oppos­ite the main gate of Arkwright’s Mill at Cromford, means by its loc­a­tion. There are other more subtle ques­tions though. What did draw­ing a second water chan­nel through the Derwent Valley mean for land use and access­ib­il­ity? Why was Willersley Castle, a grand house that Arkwright built for him­self, placed where it was? How did it relate to the church he built? If you want to know why a mill owner would want to build a church for his work­ers then, as Mark Henshaw says, you have to look at his­tor­ical records too.

You can write a his­tory purely from his­tor­ical records and archives, but if you want to exam­ine the human exper­i­ence, espe­cially of humans that weren’t writ­ing much, then an Industrial Archaeology can yield a richer, more four-dimensional exper­i­ence, than Anthropology or History alone.

What does the new henge mean for Stonehenge?

Confusion at Stonehenge
Confusion at Stonehenge

Confusion at Stonehenge

I don’t know.

I think the cov­er­age at places like the BBC are good, David Gregory found it excit­ing and I thought his story was a good read. However there are too many details miss­ing from the reports to come to any con­clu­sions. That’s not a com­plaint about the cov­er­age, the mass-media isn’t an archae­olo­gical journal. It’s not even a gripe about pub­lic­a­tion by press-release because Mike Parker Pearson showed last year that news leaks out, so why not give the brief details out properly?

On the other hand the Birmingham team are look­ing at the land­scape and, from read­ing the reports, I’ve no idea where this new site is in rela­tion to Stonehenge. It’s almost cer­tainly in sight of Stonehenge, but then the land­scape round there is littered with bar­rows, Bronze Age burial mounds. The loc­a­tion will affect how we see the land­scape. This henge isn’t to be con­fused with Bluestonehenge, the site found by the river Avon near Stonehenge last year. It’s also not Woodhenge, des­pite being made of wood, because that’s a dif­fer­ent site near Durrington Walls, which is another site that has been in the news in recent years.

There’s not a lot I can say about the astro­nomy of this henge either. It could be aligned to the sum­mer sun­rise, but I can’t tell because the dia­gram doesn’t say which way north is. Also look­ing at the dia­grams, the stone circle seems to have entrances facing one axis and the tim­ber circle an entirely dif­fer­ent align­ment. In fact, the entrance to the wooden circle seems to be facing stones. To me, that sug­gests at least two phases to the monu­ment. I ima­gine that there’ll be some sort of test excav­a­tion along sim­ilar lines. If you want to take your time plan­ning an excav­a­tion it’s a very sens­ible idea not to flag up the loc­a­tion in the news.

Ground Penetrating Radar by Ben Urmston

Ground Penetrating Radar by Ben Urmston

The con­fu­sion that this find­ing is going to cause will be huge fun for Stonehenge watch­ers. The equip­ment they’re using is Ground-penetrating RADAR. This used to be rub­bish, some­thing you’d only use in an urban loc­a­tion where you got a good sig­nal, but as with everything involving a micro­pro­cessor it’s advanced massively. It means that there’s huge swathes of land where some com­pletely unex­pec­ted things will be found. In some­where as busy as the Stonehenge land­scape there has to be much more than this wait­ing to be dis­covered. It’ll raise some awk­ward ques­tions for archae­oastro­nomers, because des­pite there being align­ments will these newly dis­covered struc­tures have blocked the view?

The excit­ing thing about this work is that it shows not only to we not have all the answers, we don’t even have all the questions.

Photo credit: Ground Penetrating Radar photo by Ben Urmston.

Survey: How do you know you’re doing it right?


Archaeological sur­veys tend to be samples of a site. How do you know you’re doing it right when you can’t see the arte­facts you’ve missed? Couldn’t you be miss­ing large chunks of inform­a­tion because it’s not what you’re expect­ing to see? David Pettigrew guest blogs at The Archaeology of the Mediterranean World,

AoB Blog goes live (or what I’m doing on my summer holidays)


AoB Blog logo

AoB Blog is now live at aobblog​.com. The design looks sim­ilar to this site, and that’s partly because I’ve been using this site to test some code. It’ll be part of the web pres­ence I’m build­ing for the Annals of Botany. Surprisingly there is some archae­olo­gical rel­ev­ance. Papers are open to non-subscribers after a year and some of those are archaeobotanical.

I’ve emailed a couple of people about an inter­est­ing story on reburial. I’m try­ing to get a bit bey­ond the press release, but I’m not sure if that will hap­pen soon as they’re both likely to be very busy.

In the mean­time I’ve blogged Moving bey­ond the ‘One-dinosaur-fits-all’ model of sci­ence com­mu­nic­a­tion at AoB Blog. It prob­ably has some rel­ev­ance to archae­olo­gical / his­tor­ical out­reach too.